1. Field of the Invention
The invention relates to a tire pressure monitoring device, more particularly to a tire pressure monitoring device that includes a high gain antenna.
2. Description of the Related Art
FIG. 1 illustrates a conventional tire pressure monitoring device 9 that includes a circuit board 92, a sensor 94, a controller 93, and a helical antenna 91. The sensor 94, the controller 93, and the helical antenna 91 are mounted on the circuit board 92.
The aforementioned conventional tire pressure monitoring device 9 is disadvantageous in that the helical antenna 91 has a large size. Moreover, the controller 93 is disposed close to and is a source of interference for the helical antenna 91, thereby decreasing the antenna gain of the helical antenna 91.
From experimental results, when the helical antenna 91 of the conventional tire pressure monitoring device 9 is operated at a carrier frequency of 434 MHz, the helical antenna 91 achieves an average antenna gain of −17 dBi.
FIG. 2 illustrates measured three-dimensional radiation patterns 90 of the helical antenna 91 of the conventional tire pressure monitoring device 9.
FIG. 3 illustrates measured radiation patterns (Eθ, Eφ) in the x-z plane of the helical antenna 91 of the conventional tire pressure monitoring device 9.
FIG. 4 illustrates measured radiation patterns (Eθ, Eφ) in the y-z plane of the helical antenna 91 of the conventional tire pressure monitoring device 9.
FIG. 5 illustrates measured radiation patterns (Eθ, Eφ) in the x-y plane of the helical antenna 91 of the conventional tire pressure monitoring device 9.